| Message ID | 20200211135256.24617-26-joro@8bytes.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Linux as SEV-ES Guest Support | expand |
On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro@8bytes.org> wrote: > > From: Joerg Roedel <jroedel@suse.de> > > Handling exceptions during boot requires a working GDT. The kernel GDT > is not yet ready for use, so install a temporary boot GDT. > > Signed-off-by: Joerg Roedel <jroedel@suse.de> > --- > arch/x86/kernel/head_64.S | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > index 4bbc770af632..5a3cde971cb7 100644 > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -72,6 +72,20 @@ SYM_CODE_START_NOALIGN(startup_64) > /* Set up the stack for verify_cpu(), similar to initial_stack below */ > leaq (__end_init_task - SIZEOF_PTREGS)(%rip), %rsp > > + /* Setup boot GDT descriptor and load boot GDT */ > + leaq boot_gdt(%rip), %rax > + movq %rax, boot_gdt_base(%rip) > + lgdt boot_gdt_descr(%rip) > + > + /* GDT loaded - switch to __KERNEL_CS so IRET works reliably */ > + pushq $__KERNEL_CS > + leaq .Lon_kernel_cs(%rip), %rax > + pushq %rax > + lretq > + > +.Lon_kernel_cs: > + UNWIND_HINT_EMPTY I would suggest fixing at least SS as well.
On Tue, Feb 11, 2020 at 02:29:24PM -0800, Andy Lutomirski wrote: > On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro@8bytes.org> wrote: > > + /* GDT loaded - switch to __KERNEL_CS so IRET works reliably */ > > + pushq $__KERNEL_CS > > + leaq .Lon_kernel_cs(%rip), %rax > > + pushq %rax > > + lretq > > + > > +.Lon_kernel_cs: > > + UNWIND_HINT_EMPTY > > I would suggest fixing at least SS as well. You are right, that is cleaner. Initialized DS, ES, and SS to __KERNEL_DS here too. Regards, Joerg
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 4bbc770af632..5a3cde971cb7 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -72,6 +72,20 @@ SYM_CODE_START_NOALIGN(startup_64) /* Set up the stack for verify_cpu(), similar to initial_stack below */ leaq (__end_init_task - SIZEOF_PTREGS)(%rip), %rsp + /* Setup boot GDT descriptor and load boot GDT */ + leaq boot_gdt(%rip), %rax + movq %rax, boot_gdt_base(%rip) + lgdt boot_gdt_descr(%rip) + + /* GDT loaded - switch to __KERNEL_CS so IRET works reliably */ + pushq $__KERNEL_CS + leaq .Lon_kernel_cs(%rip), %rax + pushq %rax + lretq + +.Lon_kernel_cs: + UNWIND_HINT_EMPTY + /* Sanitize CPU configuration */ call verify_cpu @@ -480,6 +494,18 @@ SYM_DATA_LOCAL(early_gdt_descr_base, .quad INIT_PER_CPU_VAR(gdt_page)) SYM_DATA(phys_base, .quad 0x0) EXPORT_SYMBOL(phys_base) +/* Boot GDT used when kernel addresses are not mapped yet */ +SYM_DATA_LOCAL(boot_gdt_descr, .word boot_gdt_end - boot_gdt) +SYM_DATA_LOCAL(boot_gdt_base, .quad 0) +SYM_DATA_START(boot_gdt) + .quad 0 + .quad 0x00cf9a000000ffff /* __KERNEL32_CS */ + .quad 0x00af9a000000ffff /* __KERNEL_CS */ + .quad 0x00cf92000000ffff /* __KERNEL_DS */ + .quad 0x0080890000000000 /* TS descriptor */ + .quad 0x0000000000000000 /* TS continued */ +SYM_DATA_END_LABEL(boot_gdt, SYM_L_LOCAL, boot_gdt_end) + #include "../../x86/xen/xen-head.S" __PAGE_ALIGNED_BSS